The invention relates to a method of rough-honing the circumferential surface of a bore.
Based on the possible metal-removing capacities and tool lives, it has already been proposed that fine-boring be replaced by rough-honing. In this way, the advantages of the honing process can be more fully utilized. In order, however, to achieve quality corrections in terms of angularity and positional precision comparable to those when using fine-spindle-machining, it is not possible to transfer the normal degrees of freedom for a honing tool and workpiece to rough-honing.
The concept of employing rough-honing instead of fine boring thus provides for a fixed alignment of the tool axis as well as fixed clamping of the workpiece. Based on the index position, the workpiece can be received with sufficient accuracy relative to the tool axis. Based on top and bottom tool guidance, a rigid alignment of the tool at the specified position of the bore can be achieved, with the result that the angular axial position of the tool is stable. The difference in regard to position and angular position of the tool axis to the pre-machined bore axis represents the required correction potential.
At the start of the rough-honing process, the honing stones only partially work the circumferential surface of the bore. As more and more material is removed, cutting expands to the full area of the entire bore. Since generally a varying amount of material is removed locally, a new bore center is created which is identical to the tool center. During the initial cut, only a few honing stones transfer the contact pressure to the bore wall. This therefore requires a form-locking feed device, i.e., an incremental feed. The feed functions consist in the intermittent feed motion, composed of the parameter defined from the feed phase and the feed pause interval in which the previously developed feed pressure diminishes.
This method of rough-honing, which is known from the article by U. Klink/G. Flores “Honing CGI Cylinder Bores” [Honen von Zylinderbohrungen aus GGV] in the journal WB. Werkstatt und Betrieb, Volume 133, 2000, Issue 4, Carl Hanser Verlag, Munich, can be implemented only with those workpieces in which very specific requirements are met in regard to accessibility of the bores, with the result that significant limits are placed on the method's scope of application. It is usable for continuous bores but not for blind-hole bores, which are predominantly encountered in, for example, cylinder barrels.
Therefore, there is a need for a technique of rough-honing the circumferential surface of a bore that has broader applicability.